Analog Audio IO Specs

[laenzi]

Sorry for asking stupid questions.

I could not find much information about the audio I/O specs.
Are they asymmetric I/O?
Is there a reference implementation for using the IO on stage?
What are the S/N of the DAC and ADC?
What are max input voltage level?
What happens, if by mistake 48V phantom power is attached to the output?

Best Regards

[Manysounds]

Phantom power would most likely fry the board but it would be difficult to make that connection without intentionally making a balanced or XLR connection. The ADC inputs and outputs are unbalanced (as are all manufactured ADC chips). So no worries there, unless you do it to yourself somehow. Any balanced connection would have to go through a balanced-to-unbalanced conversion, like a transformer or something, so phantom power should be blocked from the Daisy.
The audio outputs are not DC coupled so you can’t output CV voltages that way but you can output asymmetrical audio streams, it’s just that there is a “I’m not DC coupled” high pass filter on extremely low frequencies.
I have not been able to find exact information on the S/N ratio, THD, or reference voltages. It would be nice to know that if I output a -18dBFS sine wave that it would be 1v dbu, but I don’t. I thought I read somewhere that the noise and THD varied a bit from chip to chip but I can’t for the life of me find that link.
I have not done any tests on my bench to answer any of these questions but the input distorts nicely instead of nastily but again, I don’t know what the headroom is.
I know I didn’t answer your questions, except maybe the phantom power thing. To pull audio from the Daisy when using XLR I go through a passive transformer direct box so I’m not concerned. 1/4 balanced line inputs into mixers rarely (if ever) pass phantom power. Unbalanced connections cannot carry phantom.

[tunagenes]

@Manysounds

I read somewhere that the noise and THD varied a bit from chip to chip but I can’t for the life of me find that link.

Here’s a post from @shensley that summarizes the history and status of the various ‘codecs’ (combined ADC and DAC) used in different revisions of the Daisy Seed and related products, giving their chip part number and mostly talking about SNR and ‘noise floor’:

Rev5 seed producing ~13dB higher noise floor

To address your question, I feel some Daisy-History is necessary, but the short-version is that the difference in noise floor is related to the codec installed on the board. The original release of Daisy Seed (rev4) had the AK4556 codec installed. The AKM factory that manufactured that codec burned down due to a fire in 2020. Unfortunately, the end result was the part being discontinued, with no plans of continuing to manufacture it. In order to keep Daisy alive despite this, and to be able to…